Development of Hyphenated Techniques with ETAAS for Determination of Ultra-Traces of Manganese and Vanadium and Their Speciation in Environmental Samples

The technique of in-situ electrodeposition, coupled with ETAAS (ED ETAAS), has been developed for determination of ultra-traces of manganese and vanadium in environmental samples. The goal is electrodeposition of ultra traces of analyte onto the renewable Pd-coated substrate at optimized conditions of voltage, time of deposition and pH of sample solution prior to measurement by ETAAS. The characteristic masses in the determination of manganese and vanadium are superior to those of conventional ETAAS (Conv-ETAAS) measurements. The detection limits for the interested elements have been improved over those of Conv-ETAAS, with precision of the determinations in the range of 1-3 RSD%. In this work, a technique was developed for speciation of these elements in the environmental samples. Therefore, a solid phase extraction method, coupled with ETAAS or ED-ETAAS, has been investigated for this purpose. The results showed that it could be a fast and sensitive method for manganese and vanadium speciation. A C_18 cartridge, modified with sodium diethyldithiocarbamate (SDDTC), has been employed for the selective separation of manganese (VII) ions from other associated metal ions, especially manganese (II), even at much higher concentrations, followed by ED-ETAAS determination. To separate vanadium (IV) from vanadium (V), a modified membrane disk loaded with disodium ethylenediaminetetraacetic acid (Na_2EDTA) was used to trap both vanadium species, then, the vanadium (IV) ion was eluted selectively and ED ETAAS was used for determination.